Fluid Power Provides Thrills and Mystery

What is in this article?:

Creativity and technical expertise are the tools designers use to harness the benefits of fluid power to work behind the scenes at theme parks around the world.

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In the past, our annual “Fluid Power on Vacation” theme has revealed behind-the-scenes technology at major attractions in the U.S. However, theme parks and other entertainment attractions certainly are not limited to North America — and neither is the successful application of fluid power. So this year’s feature article examines innovative use of hydraulic and pneumatic technologies in entertainment attractions both here and overseas.

The first case studies focus on thrill rides, Millennium Force and Power Tower, both at Cedar Point, Sandusky, Ohio. Speed and height incite fear and thrills into the participants of these attractions, while pneumatic technology is at work to help ensure their safety. Millennium Force, like most roller coasters, is primarily mechanical, so it makes only limited use of fluid power. But that limited role involves visitor safety and throughput — top priorities at Cedar Point. On the other hand, Power Tower would not be possible without pneumatics, which is the very essence of this stratospheric thrill ride.

Subsequent coverage travels overseas to reveal attractions in the U. K. and Thailand. In both cases, hydraulics technology is called upon to pull off illusions that leave visitors wondering, “How’d they do that?”

Speed, frightening heights, and pneumatics

Officials at Cedar Point use words such as tallest, fastest, and steepest to describe their newest roller coaster, Millennium Force. And no wonder. With its 300-ft drop, 92-mph top speed, and 80° slope, it certainly is a record breaker. In fact, Cedar Point officials mention at least ten roller coaster records shattered by the Millennium Force.

But even before riders board the Millennium Force, pneumatics is at work expediting the loading and unloading of passengers. The Millennium Force routinely operates with three trains — each train carries as many as 36 people — and can bring thrills to approximately 1600 riders per hour.

When a coaster train arrives at the loading station, 18 pairs of closed gates keep riders a safe distance away from the track. At the appropriate time, pneumatic cylinders open all the gates simultaneously, and riders climb into the train. The gates are opened by two 2-in. bore, 12-in. stroke air cylinders. The cylinders are connected to a mechanical linkage that opens all 18 pairs of gates simultaneously — one cylinder opens the left-hand gates, the other opens the right-hand gates.

Pneumatics allows regulating opening and closing speed independently through flow-control valves. Also, opening and closing torque is controlled through a pressure regulator. Precise control of pressure provides enough torque to actuate the gates, but a relatively low operating pressure — coupled with air’s compressibility — provides enough “give” to open and close the gates gently and safely.

Naturally, the faster a coaster goes, the tougher it can be to stop. The challenge becomes how to stop it quickly, smoothly, and reliably. Traditional methods of using high-friction pads just won’t cut it. Instead, the Millennium Force is brought to a halt by permanent magnets.

Tim Smith, logistics supervisor at Cedar Point, explains that fins on both sides of a coaster train pass through a series of permanent magnets as the train approaches the unloading station. These magnets are mounted on both sides of the track, and magnetic fields act on the fins to slow down the train. “The faster the train is moving, the stronger the deceleration force imposed by the magnetic fields,” says Smith. “It’s like moving your hand through water: that faster you try to move your hand, the greater the resistance from the water. But if you move your hand slowly, you’ll feel very little resistance. This is how the electromagnets work. Trains entering the braking section at different speeds and with different loads will exit at roughly the same speed.”

The train then coasts to a second set of magnets that bring it to a halt. These magnets are strong enough to hold the train in place, but because they are permanent magnets, they must be removed to allow the empty train to move forward to the loading station. Again, pneumatic technology answers the call. In this case, once all passengers have exited the unloading area, an operator energizes a set of pneumatic cylinders that moves the magnets away from the train. This allows it to move forward to the loading station.

Smith points out that these are diaphragm-type cylinders. “The rod of each cylinder is attached to a diaphragm, rather than to a sliding piston. It’s the same type of cylinder used in truck brakes. It has no piston rings to wear out or leak, and is virtually maintenance free.”

In addition, pneumatics is used indirectly for the passenger restraint system. Passengers are restrained by a seat belt and cushioned lap bar. This lap bar is held in place mechanically and released electrically. When a train enters the loading-unloading station, a pair of pneumatic cylinders raises a pair of contacts that completes a circuit to release the restraint system. Before the train leaves the loading-unloading station, the cylinders retract to break the circuit, thereby locking the restraints in place. Each train also has a mechanical override to release the restraint system in the unlikely event of a power failure or other type emergency.

Smith says, “Everything on this attraction is designed to be fail-safe. But what’s nice about having pneumatics running so many systems is that the power from the compressed air stored in the system allows us to operate for several cycles even if electrical power has not been restored. The permanent magnets themselves, of course, require no external power of any kind.”